fix(docs): Add environment input type for workflow_dispatch

[FidelusAleksander]

Why:

Environment input type is supported for workflow_dispatch event triggers for a long time. It's confusing that it isn't in this part of the documentation.

It was there before but was wrongly removed in #25436

Related to: #25938
Closes: #25938

What's being changed (if available, include any code snippets, screenshots, or gifs):

Check off the following:

• I have reviewed my changes in staging, available via the View deployment link in this PR's timeline.

  • For content changes, you will also see an automatically generated comment with links directly to pages you've modified. The comment won't appear if your PR only edits files in the data directory.

• For content changes, I have completed the self-review checklist.

[github-actions]

Automatically generated comment ℹ️

This comment is automatically generated and will be overwritten every time changes are committed to this branch.

The table contains an overview of files in the content directory that have been changed in this pull request. It's provided to make it easy to review your changes on the staging site. Please note that changes to the data directory will not show up in this table.

---

Content directory changes

You may find it useful to copy this table into the pull request summary. There you can edit it to share links to important articles or changes and to give a high-level overview of how the changes in your pull request support the overall goals of the pull request.

Source	Preview	Production	What Changed
actions/using-workflows/workflow-syntax-for-github-actions.md	fpt ghec ghes@ 3.10 3.9 3.8 3.7 3.6 ghae	fpt ghec ghes@ 3.10 3.9 3.8 3.7 3.6 ghae

---

fpt: Free, Pro, Team
ghec: GitHub Enterprise Cloud
ghes: GitHub Enterprise Server
ghae: GitHub AE

[cmwilson21]

@FidelusAleksander Thanks so much for submitting a PR! I'll get this triaged for review ⚡

[garysassano]

From the github-workflow schema:

"type": {
  "description": "A string representing the type of the input.",
  "$comment": "https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#onworkflow_dispatchinputsinput_idtype",
  "type": "string",
  "enum": [
    "string",
    "choice",
    "boolean",
    "number",
    "environment"
  ]
},

[SiaraMist]

Thank you for fixing this @FidelusAleksander! ⚡ Our repository is currently frozen during GitHub Universe, but I'll add the Merge after freeze label and we should get your PR merged next week.

[github-actions]

Thanks very much for contributing! Your pull request has been merged 🎉 You should see your changes appear on the site in approximately 24 hours. If you're looking for your next contribution, check out our help wanted issues ⚡